In 2009, after three decades as the Vatican's most brilliant (and most obstinate) Latinist, Friar Reginald Foster was finally ousted from his longtime role as Secretary of Briefs to Princes—the Pope's chief diplomatic translator, as well as custodian of the Lexicon Recentis Latinitatis, the Church's guide to modern Latin.

Rumors at the time—all true—had Foster upbraiding fellow holy men for their deficiencies in Latin, giving classes for free (annoying to the Church's academic budgeters), going AWOL from in situ duties so he could minister to the poor, and buying bus tickets for prostitutes. ("Every prostitute and bum in Rome spoke Latin," Foster famously said.) Among the cardinals of the Holy See and younger clerics on the make, Foster's demotic sympathies and distrust of papal finery made him a political liability. After he made an outspoken appearance in Bill Maher's atheistic broadside Religulous, Foster found himself nudged to take early retirement in his home state of Wisconsin. He's still in Milwaukee, speaking Latin with Catholics and pagans alike.

If I were the boss I wouldn't be living there. Jesus would probably be out in some barracks here in the suburbs of Rome.... He might have been born on July third. These are all nice stories.... You just have to live and die with their stupid ideas. Talk about "cafeteria Catholics."

I raise the figure of Reginaldus (as he is known to his many Latin-spouting protégés) because the very things that galvanized Benedict's Vatican against Foster are shaping American conservatives' response to Pope Francis on his first visit to the United States this week. Francis is, in Foster's happy phrase, now "boss," and has declined to live in the lavish Papal apartments, preferring instead a garret in the Vatican guesthouse. For his 77th birthday, Pope Francis invited a homeless man and his dog to breakfast. For a brief period, it even appeared our new cool uncle of a Pope would dispense with the Popemobile and instead cruise the autostrada in a 1984 Renault. (Francis arrived at the White House Wednesday in a shiny but aphid-sized Fiat 500.)

This focus on compassion and social justice has blackened Francis in the eyes of right-wing American Catholics, especially the six of them who made GOP primary bids this year.

Like Foster, Pope Francis is not squeamish about "untouchables" (it remains truly remarkable how much some Vatican-dwellers loathe the grimy Roman underclass). Witness his famous foot-washings among Muslims, women, and prisoners. Pope Benedict remained a powerful obstructionist in the prosecution of child rape while simultaneously "investigating" American nuns for allegedly secular sympathies. Francis, meanwhile, has signaled his alliance with the Church's nuns—the ones who do the educating, the alms-giving, and none of the raping—by closing the Benedictine investigation with an encomiastic conclusion: Nuns, the final report signed by Cardinal Gerhard Mueller assures us, remain "essential for the flourishing of religious life in the church." Francis has made common cause with these American sisters, emphasizing shared priorities of compassion and social justice.

Curiously, this focus on compassion and social justice has blackened Francis in the eyes of right-wing American Catholics, especially the six of them who made GOP primary bids this year. Citing the Pope's (apparently incomprehensible) concerns about poverty, about sicknesses of the body and of the Earth, and about child refugees, the Republican party line runs simple and straight. Chris Christie told CNN that Francis' "infallibility is on religious matters, not on political ones." Critiquing the pontiff's concerns about anthropogenic climate change, Rick Santorum rivaled St. Paul for condescension: The Church, Santorum said, should "focus on what we're really good at, which is theology and morality." (Several thousand victims of clerical molestation might well question whether the Church is indeed "really good" at morality.)

Slate's William Saletan and others have noted that Republicans are very pleased to acknowledge the Church as scientific arbiter whenever a churchman starts castigating "abortifacients," but chide the Pope for "not being a scientist" when he inveighs against carbon emissions.

Other Republicans have alit on similar points of casuistry: The Pope's infallibility "does not extend to political issues, like the economy," Marco Rubio told Fox News. "On economic issues, the pope is a person." Jeb Bush maintains: "I don't get economic policy from my bishops or my cardinals or my pope.... Religion ought to be about making us better as people and less about things that end up getting in the political realm."

When conservative theocrats start worrying aloud about an erosion between church and state, we have indeed arrived at a very interesting morning in America.

One of the many ironies in the two-step performed by GOP papists is the notion that the pope is not a politician. Really? He heads a nation-state and acts as diplomatic arbiter in peace talks, and his predecessors anointed emperors and kings; led armies into battle; tortured political rivals; and sired more children than Charlemagne. The Holy See has migrated away from and back to Rome over the past 1,700 years, but never was it an apolitical state.

When conservative theocrats start worrying aloud about an erosion between church and state, we have indeed arrived at a very interesting morning in America.

Moreover, Santorum and Rubio and Jindal all favor faith-based policy in sex education and women's reproductive health—often relying on bad Vatican science to make their arguments—so the casuistry sort of dissipates on even cursory inspection. For his part, Pope Francis is working a quiet Catholic miracle: His words on open relations between the U.S. and Cuba, on climate change, or global poverty, or the plight of refugees, represent a rhetoric that unites deeply personal faith with a broader social conscience—a consummation hitherto unseen in the modern Catholic Church, where so-called "macro" problems are so often treated as abstract points of inquiry, and private worship is construed primarily as the regulation of sexual behavior. (John Paul II, Benedict's very popular predecessor, gave 129 lectures on the "theology of the body," where lucky acolytes came to hear a virgin talk about the 129 different ways he had never had sex.) During the Reformation, the Church of Rome rebooted itself in baroque splendor to stave off obsoletion. Now, Pope Francis is unifying two strands in Catholic life by insisting on a fuller definition of "pro-life"; i.e., to be truly pro-life, one must concern oneself with how zygotes fare beyond gestation and delivery. In personal faith and social conscience alike, our pontiff holds fast to the ideals of his namesake, living in apparent humility and preaching it all the more credibly in public. Rare among popes, Francis seems to have the political and personal imagination to re-invigorate an older, purer tradition—by breaking with its more degraded attitudes.*

Friar Foster, too, was seeking something older, purer, less theatrical, and more compassionate. Unlike Foster, Francis is now boss, and hard-liners are unsettled to see the pontifical focus shift from the sexual to the social. "Fair-weather Catholics," in the 1960s, meant Catholics who had reconciled their consciences with birth control. In 2015, it means Catholics who demonize nuns and rebuff social solutions to poverty and the ruin of the Earth—a planet that Francis calls "our sister." While the GOP tangles itself in casuistic rhetoric, the latest Vicar of Christ continues to fascinate and appall Americans—re-building the quaky foundations of the Church as he goes along.

*UPDATE: September 24, 2015 — A typographical error in a previous version of this article suggested that Pope Francis is a Franciscan. (He is a Jesuit.)